This study analyses the development of a tobacco-control agenda in Brazil following the country's participation in the World Health Organization Framework Convention on Tobacco Control (WHO-FCTC). This process started with the diplomatic negotiations for the participation of Brazil in the treaty, in 2003, and its ratification by the National Congress, in 2005, and was marked by substantial controversies between public health players, who are accountable for tobacco-control actions, and the high echelon of Brazilian diplomacy, emissaries of the tobacco industry, representatives of small tobacco farmers from the Southern region of the country, congress representatives, senators and ministers. The study is based on the contributions of John W. Kingdon on the development of an agenda for the formulation of public policies. It took into account secondary references, legislative and institutional sources from the 1995 to 2005 period. It concluded that the association of tobacco-related healthcare actions by technically skilled officials, the involvement of the high echelon of the Ministry of Foreign Affairs (policy flow), the initiative for the establishment of the WHO-FCTC (problem flow), and the existence of a favorable environment in both, executive and legislative (political flow), opened a window of opportunity for WHO-FCTC ratification and its inclusion in the government decision agenda.